中文（繁體）
中文（简体）
English
S4 Chemistry: Rate of Reaction (Paper 4)
S4 Chemistry: Rate of Reaction (Paper 4)
Paper 4 is the error-repair and mixed review set: four grams of magnesium falling to one gram gives zero point zero three grams per second, ninety cubic centimetres in forty-five seconds gives two, zero point four zero mole in eighty seconds gives zero point zero zero five zero mole per second, and zero point zero two mole per cubic decimetre per second over twenty seconds gives zero point four zero. The middle items split one curve into two stages at one point two and zero point six cubic centimetres per second, double the rate every ten degrees to turn forty seconds into ten, and take two hundred cubic centimetres of zero point zero five molar acid to one hundred and twenty cubic centimetres of hydrogen. The challenge items run zero point zero one five mole of acid at five times ten to the minus four per second to thirty seconds and one hundred and eighty cubic centimetres of gas, compare an opening rate of two point four with an overall one point six for a factor of one and a half, and close with the error of swapping mass and time.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S4 Chemistry: Rate of Reaction |
| Level | Four basic, three advanced, two challenge and one error-repair item |
02 Questions (10 items)
- Foundation4.0 g of magnesium ribbon is added to dilute hydrochloric acid and 1.0 g is left after 100 s. Find the average rate.
- FoundationA reaction collects 90 cm3 of gas in 45 s. Find the average rate.
- Foundation0.40 mol of reactant is used up in 80 s. Give the average rate in mol per second.
- FoundationA reaction runs at 0.02 mol dm-3 s-1. How far does the concentration fall in 20 s?
- IntermediateA reaction collects 36 cm3 of gas in the first 30 s and 18 cm3 more in the next 30 s. Find the average rate of each stage.
- IntermediateA reaction takes 40 s at 20 degrees Celsius. If the rate doubles for every 10 degree rise, how long does it take at 40 degrees Celsius?
- Intermediate200 cm3 of 0.050 mol dm-3 hydrochloric acid reacts with excess magnesium. Find the maximum volume of hydrogen at 24 dm3 per mole.
- Challenge50 cm3 of 0.30 mol dm-3 acid is used at 5.0 x 10-4 mol per second. How long does it last, and what volume of carbon dioxide results if two moles of acid give one mole of gas at 24 dm3 per mole?
- ChallengeIn one run 24 cm3 of gas is collected in the first 10 s and 96 cm3 in the whole 60 s. How many times faster is the first stage than the overall average?
- Error redoError repair: 0.60 g of magnesium reacts completely in 30 s and a student answers 30 divided by 0.60 equals 50 g/s. Give the correct rate and say what went wrong.
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 0.03 g/s | Four grams minus one gram leaves three grams, and three grams over one hundred seconds is zero point zero three grams per second. |
| 2 | 2 cm3/s | Ninety cubic centimetres divided by forty-five seconds gives two cubic centimetres per second. |
| 3 | 0.0050 mol/s | Zero point four zero mole divided by eighty seconds gives zero point zero zero five zero mole per second. |
| 4 | 0.40 mol dm-3 | Rate times time is zero point zero two times twenty, which is zero point four zero mole per cubic decimetre. |
| 5 | 1.2 cm3/s in the first stage and 0.6 cm3/s in the second. | Thirty-six over thirty is one point two and eighteen over thirty is zero point six, so the second stage is slower because less reactant is left. |
| 6 | 10 seconds | Going up to thirty degrees halves the time to twenty seconds, and up to forty degrees halves it again to ten seconds. |
| 7 | 120 cm3 | Zero point zero five molar times zero point two zero cubic decimetres gives zero point zero one mole of acid, which makes half that in hydrogen, and half of zero point zero one times twenty-four thousand is one hundred and twenty cubic centimetres. |
| 8 | 30 seconds, then 180 cm3 of carbon dioxide. | Zero point three zero times zero point zero five zero is zero point zero one five mole, which lasts thirty seconds at five times ten to the minus four per second, and half of it times twenty-four thousand is one hundred and eighty cubic centimetres. |
| 9 | 1.5 times | Twenty-four over ten is two point four and ninety-six over sixty is one point six, so the first stage is one and a half times faster than the overall average. |
| 10 | 0.02 g/s, because the time was divided by the mass instead of the mass by the time. | Rate is change in mass divided by time, so zero point six zero over thirty is zero point zero two grams per second, and fifty comes from turning the fraction upside down. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Book an S4 Chemistry tutor Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.
